Transpiration Essay Example

with an increased light intensity cell expansion, significantly affect the results.On further investigation it transpires that 1% of water uptake is used for photosynthesis and the same amount for building protoplasm. Ninety-eight percent is lost via 'transit'. Thus the possible resultant change in photosynthesis with an increased light intensity will not be significant so, the rate of water loss can be calculated by the distance a bubble moves in a potometer.

The variable, which needs to be adjusted, is the light intensity, with the limited facilities available to me, the best way to do this is to use a lamp and move it closer and further away form the plant, but this would also adjust the temperature that the plant is in, i.e. increased as the source (lamp) moves closer.The intensity of the light will be measured using a luxmeter, this will be kept at a stationary position and angle on the plant, so that any discrepancies will be nullified i.e. if the angle of the luxmeter is not optimal to obtain the current reading, then it will not be optimal for all the readings, thus the inaccuracy will be constant and therefore irrelevant.The rate at which water is lost is not only affected by the intensity of the light, it is affected by other factors, which affect transit and are claimed to be external and internal factors. These factors need to be minimal so that the only variable, which is adjusted, is light intensity.

External Factors Humidity - This is concentration of water vapour in the air, as this affects the water potential gradient both outside the leaf and within the leaf. If the air is

dry the potential gradient is great thus temperature increases. Temp - The higher the temperature, the greater the kinetic energy of the molecules thus increasing transpiration. The surrounding air can also hold more water, so thus it increased the potential gradient.

Air Movement - If a layer of moist air around the leaf is constantly blown away, then this maintained the potential gradient thus increases the rate of transpiration. Light intensity - See HypothesisInternal FactorsThere are a number of anatomical and morphological differences between plants/leaves, which influence transpiration rate i. e.Leaf Area - A proportion of the water loss via cuticle thus increase in area leads to increase in transpiration irrelevant to concentration of stomata (which will also increase as leaf area increases Cuticle - This is a waxy covering outer leaf surface, which eliminates water loss. The thinner this is, the increased rate of transpiration. Stomata - The greater the number of Stomata per area, the greater the rate of transpiration.The internal factors which affect transpiration will be minimised by the use of the same leafy plant throughout the experiment, and allowing five minutes for the plant to equilibrate before introducing the air bubble.

External factors will be minimised using the following precautions. Humidity- this I assume will be constant in the lab and will not drastically alter, in the time frame of the experiment.* Temperature - will be constant in the room, but will vary as the intensity is increased, due to an inherent flaw in the way light is to be delivered. The overall temperature in the room will be controlled centrally via air-conditioning.Air movement - I will stay away from open windows.* Water

availability - The water reservoir can be constantly replenished by the reservoir in the potometer, which will be used to reset the air bubble to zero.